WO2009033548A1 - Dispositif de mesure de diaphonie et procédé associé - Google Patents

Dispositif de mesure de diaphonie et procédé associé Download PDF

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Publication number
WO2009033548A1
WO2009033548A1 PCT/EP2008/006698 EP2008006698W WO2009033548A1 WO 2009033548 A1 WO2009033548 A1 WO 2009033548A1 EP 2008006698 W EP2008006698 W EP 2008006698W WO 2009033548 A1 WO2009033548 A1 WO 2009033548A1
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WO
WIPO (PCT)
Prior art keywords
communication lines
crosstalk
lines
disturber
victim
Prior art date
Application number
PCT/EP2008/006698
Other languages
English (en)
Inventor
Mamoun Guenach
Danny Van Bruyssel
Geert Bert Maarten Ysebaert
Jochen Maes
Michael Peeters
Original Assignee
Alcatel Lucent
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Alcatel Lucent filed Critical Alcatel Lucent
Publication of WO2009033548A1 publication Critical patent/WO2009033548A1/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L27/00—Modulated-carrier systems
    • H04L27/26—Systems using multi-frequency codes
    • H04L27/2601—Multicarrier modulation systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B3/00—Line transmission systems
    • H04B3/02—Details
    • H04B3/46—Monitoring; Testing
    • H04B3/487—Testing crosstalk effects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/22—Arrangements for supervision, monitoring or testing
    • H04M3/26—Arrangements for supervision, monitoring or testing with means for applying test signals or for measuring
    • H04M3/28—Automatic routine testing ; Fault testing; Installation testing; Test methods, test equipment or test arrangements therefor
    • H04M3/30—Automatic routine testing ; Fault testing; Installation testing; Test methods, test equipment or test arrangements therefor for subscriber's lines, for the local loop
    • H04M3/302—Automatic routine testing ; Fault testing; Installation testing; Test methods, test equipment or test arrangements therefor for subscriber's lines, for the local loop using modulation techniques for copper pairs
    • H04M3/303—Automatic routine testing ; Fault testing; Installation testing; Test methods, test equipment or test arrangements therefor for subscriber's lines, for the local loop using modulation techniques for copper pairs and using PCM multiplexers, e.g. pair gain systems
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/22—Arrangements for supervision, monitoring or testing
    • H04M3/26—Arrangements for supervision, monitoring or testing with means for applying test signals or for measuring
    • H04M3/34—Testing for cross-talk

Definitions

  • the present invention generally relates to crosstalk measurement and more in particular to crosstalk measurement between multiple communication lines.
  • ADSL Asymmetric Digital Subscriber Line
  • VDSL Very high-speed Digital Subscriber Line
  • xDSL networks is subject to noise injected by external sources.
  • One particular problem is the influence of crosstalk between various subscriber lines within close vicinity. Crosstalk is the effect whereby a first subscriber line induces i ⁇ signals on a second, different subscriber line, which act as noise on that second subscriber line.
  • Such effects are especially noticed when multiple subscriber lines form part of the same cable or cable binder or when they are terminated close to each other, for instance in a Digital Subscriber Line Access Multiplexer (DSLAM) where multiple subscriber lines are terminated on the same board.
  • DSL Digital Subscriber Line Access Multiplexer
  • Noise effects can be dealt with in various ways, for instance the use of error correction codes can reduce the effects of noise.
  • error correction codes for instance Reed-Solomon
  • error codes can only recover a limited number of errors in data but are able to detect more errors.
  • the receiver may rely on other mechanisms to obtain corrected data, for instance retransmission.
  • Retransmission can be implemented explicitly, whereby a receiver asks the transmitter to resend a piece of data, or implicitly whereby the transmitter waits for a confirmation of the 0 receipt of the correct data and if no confirmation is received, the transmitter will automatically retransmit the data.
  • error correction codes and retransmission occupy additional bandwidth, hence reducing the bandwidth available for user data transmission.
  • these error codes reduce the effective speed of high bandwidth connections such as xDSL links. This could be acceptable to cope with impulse noise errors but may become a problem for long term noise effects such as upcoming subscriber lines which may take some time to initialize and establish a connection, and which may permanently induce crosstalk once they are active.
  • a crosstalk reduction system can influence all the communication lines terminated at a central node such as a Digital Subscriber Line Access Multiplexer (DSLAM) or a termination board.
  • DSLAM Digital Subscriber Line Access Multiplexer
  • crosstalk reduction or avoidance systems can influence a larger number of communication lines than the above describer error correction systems.
  • Crosstalk compensation mechanisms include vectoring, jointly optimizing transmit spectra, artificial and virtual noise spectra and other settings.
  • An example of a crosstalk compensation system and estimation is explained in European Patent Application EP 04 292 070 titled "Crosstalk manager for access network nodes".
  • crosstalk between subscriber lines is estimated based on quantitative information which is automatically gathered. This automatic gathering of information is based on monitoring changes in the condition of the communication lines such as on/off status, line state transitions or changes in noise margin.
  • This solution is able to identify strong crosstalkers which can be useful to optimize communication lines accordingly.
  • this solution is not able to determine or estimate crosstalk from weaker crosstalkers.
  • the strong crosstalkers have much more influence on victim lines than weak crosstalkers and as such the effect of the weak crosstalkers is hard to measure in this solution.
  • a crosstalk estimation device for estimating crosstalk between a plurality of communication lines, this plurality comprising one or more disturber communication lines and one or more victim communication lines and the crosstalk estimation device comprising means for receiving measured changes in operational parameters on the victim communication lines and means for changing the transmit power and/or power spectral density PSD on one or more of the victim communication lines and/or one or more of the disturber communication lines prior to measurement of the changes in operational parameters.
  • the SNR will change on other communication lines. If the transmit power and/or PSD changes on a single disturber line, all the lines which are disturbed by that line will notice a change in SNR. These changes can be measured and be reported back to the crosstalk estimation device according to the present invention, residing for instance in the access multiplexer. If a change is made to the transmit power or PSD on multiple disturber lines, the victim lines will notice a change in SNR that represents the combined effect of the changed transmit power or PSD on the disturber lines.
  • the crosstalk information related to multiple disturber lines can be estimated jointly thanks to the crosstalk estimation according to the present invention.
  • a line can be a victim and a disturber at the same time.
  • a victim line can be a disturber for another line
  • a disturber line can be a victim of another line.
  • Lowering the transmit power or PSD of a communication line reduces the influence of that communication line on other communication lines.
  • these changes are measured in a standard compliant and backwards compatible fashion through SNR measurements and the measured SNR changes can be related to the amplitude and phase of the crosstalk between various communication channels.
  • by lowering the transmit power or PSD there is at least temporarily a reduced influence from that line on the other communication lines.
  • the lowering of the transmit power of strong crosstalkers has the advantage that the crosstalk from weak crosstalkers can be observed with a larger accuracy.
  • raising the transmit power or PSD also enables determining the amplitude and phase of crosstalk between various communication lines but may have a negative impact on the other communication lines, for instance due to a stronger crosstalk influence. It is of course also possible to perform a first SNR measurement after decreasing and a second SNR measurement after increasing the transmit power, or changing the transmit power or PSD can be performed after other changes to the condition of one or more communication lines have been executed in order to avoid significant influences on the communication lines during the measurement.
  • the measured changes in SNR can be received from either a device at the same side of the communication line as the crosstalk estimation device of the present invention or from a device at the other end of the communication line.
  • the DSLAM is adapted to incorporate an embodiment of the crosstalk estimation device according to the present invention, it can change the transmit power and/or PSD on each communication line terminated at the DSLAM.
  • These changes can then be measured at the CPE side, by an SNR measuring function forming part of the CPE or coupled to the CPE.
  • the measured SNR changes are then delivered to the crosstalk estimation device of the present invention. This delivery can occur over a direct coupling between the crosstalk estimation device and the SNR measuring device or may involve communication between various devices over one or more communication lines or electric couplings.
  • receiving the changes in SNR can be done automatically, or may be the result of a request issued by the device.
  • the means for changing the transmit power and/or power spectral density PSD in the crosstalk estimation device may be adapted to change the transmit power and/or power spectral density PSD based on one or more Transmit Spectrum Shaping (TSSi) Coefficients.
  • TSSi Transmit Spectrum Shaping
  • the TSSi coefficients as defined in ITU-T G.992.3, G.992.5, G.993.2) are configured during the initialization of a communication line. These coefficients are used in the shaping of the transmit PSD and as such should be known by both transmitter and receiver. For instance, the receiver needs to know the TSSi coefficients used by the transmitter to allow measurement of the direct channel impulse response, for initialization and tracking of the time domain equalization (TEQ).
  • the TSSi coefficients are fixed once a communication line is initialized and current DSL standard specifications do not support a protocol to communicate a reconfiguration of these TSSi coefficients during show-time. In general, a change in TSSi coefficients in the transmitter without a communication to the receiver will disturb the tracking of the TEQ.
  • a first way to change the TSSi values without disturbing the TEQ is by scaling the TSSi values in amplitude with the same amount over all tones per line . This will not change the shape of the impulse response and therefore does not disturb the tracking of the time domain equalization (TEQ) if any TEQ is present.
  • the uniform scaling of the TSSi only results in a constant gain which can be tracked by the frequency domain equalizer, provided the scaling is applied smoothly, using small steps spread over time.
  • a second way to change the TSSi values without disturbing the time domain equalization (TEQ) is by changing the TSSi values by small amounts within iimits of acceptable performance degradation.
  • the means for changing the transmit power and/or PSD in the crosstalk estimation device may be adapted to change the transmit power and/or power spectral density PSD based on one or more On-Line Reconfiguration OLR commands.
  • OLR On-Line Reconfiguration
  • changing the transmit power and/or PSD during show-time becomes more flexible.
  • OLR commands provide a way to both ends of a communication line to change the current conditions of the communication line, for instance those as agreed during initialization.
  • These OLR commands can for instance be used to change the transmit power, PSD, TSSi coefficients, data rate, etc.
  • the present invention further relates to a method for estimating crosstalk between a plurality of communication lines, the plurality comprising one or more disturber communication lines and one or more victim communication lines and the method comprising the step of receiving measured changes in operational parameters on the victim communication lines and/or disturber communication lines, and the step of changing the transmit power and/or power spectral density PSD on the victim communication lines and/or the disturber communication lines prior to measurement of the changes in operational parameters.
  • the method for estimating crosstalk according to the present invention may further comprise one or more of the following steps prior to the step of receiving the measured changes in operational parameters:
  • the addition of artificial noise on one or more tones of one or more communication lines decreases the noise margin on these communication lines.
  • the data rate on the communication lines may be decreased by autonomous action of the receiver (e.g. based on Seamless Rate Adaptation (SRA) as defined in ITU-T G.992.3, G.992.5, G.993.2).
  • SRA Seamless Rate Adaptation
  • an additional noise margin is created, which can be used for coping with the extra crosstalk, generated in the case of the method using an increase of the PSD on the disturber lines, to allow the measurement of operational parameters and the reporting thereof.
  • the increased PSD is removed, and the data rate is allowed to increase back to its original value, for instance by autonomous action of the receiver. However, it may increase to a data rate higher than the original data rate or remain below the original data rate.
  • the method for estimating crosstalk according to the present invention may comprise the steps of: - reducing the data rate on one or more of the plurality of communication lines using an On-Line Reconfiguration OLR command prior to the step of receiving the measured operational parameters; and
  • the method may further be adapted in that the step of changing the transmit power and/or the Power Spectral Density PSD uses an On-Line Reconfiguration OLR command.
  • the crosstalk estimation device By introducing OLR commands for transmitter controlled changes to the data rate, transmit power and/or PSD, the crosstalk estimation device has direct control on these parameters.
  • the above described scenario where changes are based on artificial noise, and data rate changes by autonomous action of the receiver may remain stuck at a lower data rate after the SNR measurement.
  • OLR the DSLAM and CPE can be forced to return to a particular data rate, transmit power and/or PSD.
  • Fig. 1 illustrates a use of an embodiment of the device according to the present invention in a crosstalk measurement
  • Fig. 2 illustrates an embodiment of the device according to the present invention.
  • Fig. 1 illustrates a typical scenario wherein an embodiment of the crosstalk estimation device according to the present invention is used.
  • Fig. 1 shows a number of communication lines, terminated at one side in a Central Office (CO) and at various locations such as houses or office buildings, on the other side.
  • Fig. 1 shows a Digital Subscriber Line Access Multiplexer (DSLAM) 101 at the CO, a set of Customer Premises Equipment (CPE) 102i to 102 4 and a number of Digital Subscriber Lines (DSL) 103i to 103 4 connecting the DSLAM 101 respectively to the CPEs 102i to 102 4 .
  • DSL line 103i is the victim line
  • DSL lines 103 2 to 103 4 are the disturber lines.
  • the DSLAM 101 will configure the transmit power 104, 105 and 106 for transmission on the DSL lines 103 2 to 103 4 individually.
  • the CPE 102i is supposed to be able to measure the Signal to Noise Ratio SNR. Once the CPE 102i has information related to the SNR or the changes in SNR due to the changes in transmit power on the disturber lines 103 2 to 103 4) it can report such information back to the DSLAM 101.
  • the victim line 103i is influenced by the changes in transmit power on each of the disturber DSL lines 103 2 to 103 4 . Therefore, changes in SNR on victim line 103i are the result of all these changes rather than one change at a time.
  • CPE 102- 1 is able to report back information that is indicative for the total crosstalk induced on victim line 103i rather than the influence of a single disturber DSL line.
  • DSLAM 101 uses the reported information to determine the crosstalk between each pair of lines which in turn may be used to configure crosstalk compensation mechanisms at the CO side.
  • there are three crosstalkers the transmitters respectively connected to transmission lines 103 2 to 103 4 .
  • the number of transmit power or PSD configurations and the number of corresponding SNR measurements has to be chosen in such a way that the resulting estimation problem is mathematically solvable.
  • the linear set of equations enabling to estimate the crosstalk amplitudes needs to have at least as many equations as variables.
  • a typical DSLAM is connected to more than 4 DSL lines.
  • the crosstalk estimation according to the present invention can operate on more than 4 DSL lines.
  • crosstalk precompensation may run on a line termination card which typically supports many more lines.
  • the DSLAM may perform the measurement of SNR changes, which does not require additional communication over the DSL lines to report the results.
  • Fig. 2 illustrates one embodiment of the crosstalk estimation device according to the present invention.
  • a module 201 is shown, connected to a Digital Subscriber Line (DSL) 202.
  • the DSL line 202 corresponds for instance to one of the DSL lines 10S 1 to 103 4 in Fig. 1.
  • the crosstalk estimation module 201 contains a transmitter (Tx) 203 which is designed to transmit data over DSL line 202.
  • the transmitter 203 may be responsible for encoding the data in the correct format, add information related to one or more layers such as the physical layer and/or the transport layer, etc.
  • the transmitter 203 has an interface 204 which enables the reception of data for transmission.
  • transmitter 203 is only a line driver which places the data on the medium and does not add any information or does not perform any encoding of data.
  • the transmitter 203 is further connected to a PSD controller 205.
  • PSD controller 205 is able to change the Power Spectral Density (PSD) from the transmitter 203. This way, the PSD on line 202 can be changed.
  • the PSD controller 205 can be adapted with an interface to receive instructions. For instance, the interface can be connected to the receiver (Rx) 206 to receive instructions from remote sources such - -
  • PSD controller 205 may also be connected to other hardware in a DSLAM which is able to generate instructions. For instance a DSLAM may trigger the PSD controller 205 for each DSL line 202 when a new line is initialized, at regular or random time intervals to update information, upon request by a network manager platform, etc.
  • the receiver 206 is connected to the DSL line 202 and is able to interpret signals which are transmitted over DSL line 202.
  • the receiver 206 contains an interface 207 to transport received data to other parts of the device wherein module 201 is integrated.
  • the receiver 206 further contains an interface to a crosstalk estimation function 208.
  • the crosstalk estimation function 208 is able to receive reported operational parameter measurements (e.g. SNR measurements) which are received by the receiver 206 over DSL line 202 from a
  • the crosstalk estimation function may be able to use this information to estimate the crosstalk and eventually configure crosstalk compensation mechanisms in the DSLAM or CPE wherein module 201 is integrated or it may be able to deliver such information to other modules in the DSLAM or CPE.
  • PSD controller 205 may be more centralized in a DSLAM, LT card or a chipset and be adapted to control the PSD and/or transmit power of multiple transmitters in the DSLAM, LT card or chipset.
  • the crosstalk estimation function 208 may be more centralized in a DSLAM, LT card or a chipset to receive information from multiple receivers in the DSLAM, LT card or chipset.
  • one or more of the shown modules may be integrated into a single module or these modules may even be split into different modules.
  • K active subscriber lines which is made up out of K 3 subscriber lines which pertain to the vectoring group to reduce or avoid crosstalk and thereto use the precoding matrix F and K n subscriber lines which are joining.
  • K K 3 + K n subscriber lines.
  • K is equal to 4.
  • parameter F relates to the above mentioned precoding matrix
  • parameter H is a K * K channel matrix
  • parameter A is a K * K diagonal matrix which is representative for the square root of the transmit powers of the different lines
  • the parameter x is a vector of size K and consists of the M- QAM data symbols with unitary variance
  • the parameter w is the additive noise on the communication lines.
  • the precoded matrix F is an identity matrix for the K n lines which are not active yet and thus are not yet precoded. In case there is no precoding, the matrix F will be a complete identity matrix. In this particular example we will consider the victim line, for which a crosstalk estimation is performed is the line with index 0.
  • the crosstalk channels are denoted as Hg with two indices, the first indicating one of the victim lines and the second indicating the disturbed line.
  • H 0 ,i with / 1,...
  • K n indicates the respective crosstalk channels for each of the K n non- - - -
  • each row of the matrix P requires a set of transmit powers of the K n crosstalkers.
  • the selected transmit powers of the different crosstalkers have to be selected without significant changes to the powers from one row of P to another.
  • a K n -vector column ⁇ is
  • both the amplitude and the phase of the crosstalk channel must be known.
  • the phase measurement can be done similarly to the example given above, i.e. by constructing a (possibly different) invertible K n XK n P matrix.
  • the precoding matrix F may need to be altered as described in USPTO case 'Determining Channel Matrices By Correlated Transmissions To Different Channels' filed by Alcatel-Lucent on August 31 2007.
  • the example above describes the event where unprecoded lines join a (possibly precoded) group of lines.
  • the crosstalk channel measurements are updated regularly to track time variations of the channels.
  • a K d xK d P matrix similar to the one described above is constructed, where K d is the number of disturber lines from which the crosstalk channels need to be estimated.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Cable Transmission Systems, Equalization Of Radio And Reduction Of Echo (AREA)
  • Telephonic Communication Services (AREA)

Abstract

La présente invention concerne un dispositif d'estimation de diaphonie destiné à estimer une diaphonie entre des lignes de communication perturbatrices et des lignes de communication victimes. Le dispositif d'estimation de diaphonie est apte à modifier la densité spectrale de puissance PSD sur les lignes de communication victimes et/ou sur les lignes de communication perturbatrices. De plus, le dispositif d'estimation de diaphonie reçoit, sous forme de paramètres opérationnels relatifs aux lignes de communication victimes et/ou aux lignes de communication perturbatrices, des modifications mesurées permettant d'estimer la diaphonie induite sur les lignes de communication victimes et/ou sur les lignes de communication perturbatrices.
PCT/EP2008/006698 2007-09-10 2008-08-11 Dispositif de mesure de diaphonie et procédé associé WO2009033548A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
EP07291084A EP2034622A1 (fr) 2007-09-10 2007-09-10 Dispositif et procédé associé pour mesurer la diaphonie
EP07291084.7 2007-09-10

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WO2009033548A1 true WO2009033548A1 (fr) 2009-03-19

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EP3334054B1 (fr) 2010-06-01 2021-08-04 Telefonaktiebolaget LM Ericsson (publ) Procédé et agencement dans un système de vectorisation dsl
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EP2709345B1 (fr) * 2012-09-17 2015-02-25 Alcatel Lucent Procédés et dispositif pour réduire la diaphonie
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CN101388749A (zh) 2009-03-18
EP2034622A1 (fr) 2009-03-11
US20090073868A1 (en) 2009-03-19

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